Pass blobs into ValidatorStore::sign_block (#7497)

While the Lighthouse implementation of the `ValidatorStore` does not really care about blobs, Anchor needs to be able to return different blobs from `sign_blocks` than what was passed into it, in case it decides to sign another Anchor node's block. Only passing the unsigned block into `sign_block` and only returning a signed block from it (without any blobs and proofs) was an oversight in #6705.


  - Replace `validator_store::{Uns,S}ignedBlock` with `validator_store::block_service::{Uns,S}ignedBlock`, as we need all data in there.
- In `lighthouse_validator_store`, just add the received blobs back to the signed block after signing it.

testing/web3signer_tests/Cargo.toml

@@ -10,6 +10,7 @@ edition = { workspace = true }
 account_utils = { workspace = true }
 async-channel = { workspace = true }
 environment = { workspace = true }
+eth2 = { workspace = true }
 eth2_keystore = { workspace = true }
 eth2_network_config = { workspace = true }
 futures = { workspace = true }